Furnace stoker



- MAW; 2,201,371

FURNACE STOKER Fil ed Feb. 16, 1937 2 Sheets-Sheet l INVENTOR May 21, 1940. M. A. MAYERS FURNACE STOKER Filed Feb. 16, 1957 2 Sheets-Sheet 2 INVENTOR Ada/"fin AMaye/"J r m 44 4 ,LM

Patented May 21, 1940 FURNACE STOKER Martin A. Mayer's, Pittsburgh, Pa., assignor to Carnegie Institute of Technology of Pittsburgh,

Pittsburgh, Pa.,

a corporation of Pennsylvania Application February 16, 1937, Serial No. 125,998v

3 Claims.

stokers, the formation of this spire is inevitable in the combustion of bituminous coal and seriously interferes with the emciency of the furnace. It is one of the objects of this invention to provide apparatus by which the ill effects of this spire formation may be avoided. It is not intended to avoid formation of the spire or coke tree, but to allow this tree to so form that it will be of adextending rearwardly from the fuel admission end vantage rather than a disadvantage in the operation of the furnace.

In general, the apparatus consists of a hearth of the furnace to the back of the furnace. The hearth has openings therein so that primary air may be supplied all along the coke spire, which insures substantially complete combustion there of in an efiicient manner. The wall of the furnace opposite the fuel inlet has an abutment or batter plate against which the coke spire extends. The incoming coal is pressed against and exerts a force on the spire which is resisted by the batter'plate or abutment, and this pressure serves to agitate and break up the coke tree so that even and substantially complete combustion thereof will take place. I prefer to incline the hearth upwardly as it recedes from the fuel inlet, but this arrangement, while desirable, is not necessary.

Apparatus constructed according to my invention has advantages over conventional types of equipment used in domestic stoker systems for burning bituminous coal. The advantages are that it uses the spire itself as a means for obtaining a compact, uniform fuel bed; the spire is placed under compression at intervals, causing it to break up, and thus secures the advantages of agitation of the bed without introducing metal parts into the hot portion of the bed; and finally, it introduces primary air along the entire surface of the spire instead of merely in the narrow ring at its base. This insures proper combustion of the spire and in certain instances the furnace may be operated with natural draft, thus eliminating the expense of a forced draft fan.

In the accompanying drawings, which illusmaintained through said tubes and lengthen their trate the present preferred embodiment of the invention and in which like numerals designate like parts in the various views:

Figure 1 is a vertical longitudinal section through the lower part of a furnace embodying 5 my invention, the section being taken through the longitudinal axis of the hearth;

Figure 2 is a sectional view along the line lI-II of Figure 1;

Figure 3 is a sectional view along the line III-III of Figure 1;

Figure 4 is a sectional view along the line IV-IV of Figure 3;

Figure 5 is a view similar to Figure 2, but showing a modification of the clinker-removal arrangement;

Figure 6 is a view along the line VIVI of Figure 5;

Figure 7 is a view along the line .VIL-VII of Figure 8; and

, Figure 8 is a plan view of a portion of a modified tuyere block and support therefor constructed according to my invention.

In the drawings, there is shown the lower portion of a stoker-flred conventional hot water boiler 2, such as is in common use in domestic heating plants. The boiler has a water jacket 3,

a hearth 4, and a supporting base 5 in which there is an ash pit 6. The hearth 4 consists of a removable tuyere block 1 which rests on inclined supports 8 and 9 which may conveniently comprise two tubes, which may be connected, if desired, at each end thereof to the water jacket of the boiler so that water circulation may be useful life. It is not necessary, however, that these supports be water-cooled, as they may be constructed of an alloy which will successfully resist the heat to which they are subjected. The edges ofthe tuyere block which rest on the supports are notched to a depth sufilcient to provide a'series of air passages In between the tuyere blocks and the sides of the supports. The upper surface of the block 1 is preferably concave and the ends of the block rests on appropriate shoulders II and I2, formed on the end walls of the furnace. At the end of the tuyere block distant from the fuel inlet .or retort i3, that is, at the back of the furnace, a batter plate or'abutment I4, 50 preferably of cast iron, is secured to the rear wall of the furnace. Beneath tuyere block 1 is a wind box IE, arranged so as to supply primary air to only a portion of the length of the tuyere block. The air may be supplied to the wind box either by natural draft controlled by damper IE or the wind box may be connected to a forced draft fan (not shown) as is common practice in the art. That end of the wind box which is nearer the fuel inlet or retort l3 terminates a sufficient distance from the end of the tuyre block to allow a space within the furnace adjacent to the fuel inlet for the formation of a well defined coking region I1, far enough away from the vertical furnace walls to prevent fusion of the coke to the walls during the early portion of the off period of the furnace when the plastic zone travels toward the fuel inlet. In some designs of furnaces, it may be advisable to make the area for air admission for the retort end of the furnace greater thanat the batter or abutment end. In other words, the tuyeres at the inlet end may be of greater area than the area of the tuyeres at the batter or abutment end. In some instances, it may also be desirable to make the tuyre block without openings for a portion of its length adjacent the fuel inlet so that no air at all would be admitted to the fuel adjacent the fuel inlet. The portion of the hearth adjacent the fuel inlet through which no air passages are provided is commonly referred to as the dead plate.

Above the mouth of retort l3, a refractory covering l8 projects beyond the inner wall of the furnace. A series of small ports I9 are formed in the vertical wall of the furnace immediately above the retort and below the refractory covering l8. A slide 20 controls the port openings.

This arrangement of refractory covering and over-fire air supply insures ignition of the volatile material rising from the plastic zone ll of the retort.

If it is desired, the tuyere block may have more than two rows of openings and any number of openings can be formed in the tuyre block depending upon the design of the furnace. In Figures- 7 and 8,'I have shown a sectional tuyere block 2|, which has three rows of openings 22, 23 and 24. In this illustration, the tuyre block is shown as made up of two sections placed side by side. It is apparent that the tuyre blocks could be made in one piece and any desired number or arrangement of air passages formed therein while the block is being made or subsequent thereto. Except for the over-fire air supply through the small ports 19, all the combustion air is supplied through the tuyre blocks and from the wind box.

Ash removal may be accomplished either mechanically or manually. In Figures 1, 2, 3, and 4, I have shown conveyor screws 25 and 26 arranged adjacent the outer sides of the tuyre supports 8 and 9. The conveyor screws are rotated either continuously or intermittently as may be desired, by suitable mechanism, in a manner well known in the art. At the discharge end of the screw conveyors, the ash falls through appropriate openings 21 into the ash pans 28, located in the ash pit 6, from whence it may be removed through r the ash door 29.

the furnace walls, hearth blocks 30 of refractory material are placed. Clinkers and ash collect on these blocks and are removed through the doors 3|.

Fuel is supplied to the furnace inlet or retort 13 by means of screw conveyor 32. This conveyor, as well as the ash-removing conveyors, is driven by mechanism well known to those skilled in the artandsince such mechanism forms no part of this invention, it-need not be described.

The apparatus operates as follows: A coke spire 33 is formed soon after the furnace is put into operation. As coal is fed into the furnace through the retort 13 by screw conveyor 32, the fresh fuel immediately'adjacent the coke tree 33 in coking region I! becomes plastic as the volatilizable portions are driven off by the heat. In time, this plastic layer forms into coke and is driven forward along the upwardly inclined tuy'ere block I toward the rear of the furnace and against batter plate or abutment 14 by the pressure thereon of the incoming fuel. The fuel is fed into the furnace at intervals and the coke spire which has been formed is placed under compression at these intervals and is broken up, thus admitting air throughout the Whole mass of the coke spire and causing it to be consumed. By this means, a compact, uniform fuel bed, through which primary air may flow, is maintained, This agitation from time to time of the fuel bed by the pressure of the incoming fuel keeps the bed sufliciently agitated for proper combustion and avoids the introduction therein of metal parts such, as a poker, which is undesirable. Due to the construction of the tuyre block, primary air is introduced along the entire surface of the spire instead of merely in a narrow ring at its base, as is customary in the art. Due to the comparatively large area for air admission, the stoker may in many instances be operated very efficiently on natural draft, thus eliminating the expense of a forced draft fan.

The mechanism for driving the various con-, veyor screws, for supplying fuel to the furnace and removing fuel therefrom, and for controlling the supply of combustion air and the flue draft may be of any desired type and form no part of this invention.

The apparatus constructed in accordance with my invention is highly efiicient and economical to construct, maintain and operate.

While I have illustrated and described a preferred embodiment of my invention, it will be understood that the same is not limited thereto, but may be otherwise embodied and practiced within the scope of the following claims.

1. A bituminous coal burning apparatus for domestic hot water heating comprising a combustion chamber having a front water jacketed wall and a rear water jacketed wall, a substantially vertic l abutment on the rear wall, the front wall having a fuel inlet therethrough at a point opposite the abutment, a hearth extending from thefuel inlet to the abutment, the top of the hearth being insubstantial alignment with the bottom of the fuel inlet, said hearth having primary air passages therethrough terminating. at the top of the hearth, said hearth being of substantially the same width as the inner end of the fuel inlet, means extending from the rear wall of the furnace to the front wall for supporting the grate, a wind box secured to and supported by said means and means for forcing fuel along said hearth whereby such coke tree as may be formed by the combustion of said fuel is forced against said abutment and-disintegrated.

2. A bituminous coal burning apparatus for domestic hot water heating comprising a combustion chamber having a vertical water cooled abutment therein on one wall thereof and provided with a fuel feed opening through another wall at a point opposite the abutment, a hearth extending from the opening to the abutment, the top of the hearth being in alignment with the bottom of the fuel inlet, water cooled means extending from the rear wall of the furnace to the front wall for supporting the grate, a wind box secured to and supported by the water cooled means, means for forcing the fuel through the opening in such manner that the fuel is forced across the hearth toward and against the abutment, means for supplying primary air to the fuel along the bottom of the hearth, and means wherebyv the ash may be removed from the apparatus.

3. In a stoker fired domestic furnace for bum-' ing bituminous coking coal, a combustion cham ber, a water jacketed wall having a fuel inlety' tegrate any coke tree which 7 operation of the furnace and ash conveyor screws therethrough, a fixed hearthffor' supporting a fuel bed extending rearwardlylfrom and in substantial alignment with the {bottom of the fuel inlet, said hearth having air passages therethrough extending to the top of the hearth, means 5 be supplied to the combustion chamber and over 10 the portion of the hearth adjacent the fuel inlet,

and a substantially vertical abutment atthe rear of the hearth to which the against. which the fuel bed hearth extends and is forced to disinmay form during on each side of the hearth and parallel thereto. 

